Troops successfully raided the militant group's camps in two northeastern villages, where they managed to rescue 338 people, including nearly 200 children.
The 15-day state of emergency will allow authorities to increase security, impose a curfew, and restrict the movement of goods and people, according to an announcement on state television.
Boko Haram has killed four people in Niger as the Islamic State takes responsibility for bombing in Nigeria that killed 15 people on Friday.
Islamist militants have multiplied deadly attacks in the region, often using women and girls concealing explosives under the religious veil.
Amid intensifying attacks from the Islamist terrorist insurgency, Niger’s parliament voted to approve the deployment of troops to combat Boko Haram in Nigeria.
The Nigerian militant group struck the Niger border town of Bosso days before Niger’s parliament is set to vote on whether to send troops into Nigeria.